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High Olefin Fluid Catalytic Cracking by KBR and ExxonMobil

MAXOFIN FCC offers refiners greater returns by maximizing propylene yields from FCC feedstocks. Over 20 wt% propylene yield can be produced from gasoils by combining the effects of enhanced ZSM-5 catalysts and proprietary hardware.

This dual-riser design uses independent riser reaction conditions (cat/oil and temperatures) for heavy and light feedstocks. C4–C6 nonaromatic naphtha cuts can be recycled to the light hydrocarbon riser. In addition to processing light naphtha, the recycle riser can also accept coker and light-straight-run naphthas from the refinery. Both risers can operate at 100% gas oil/resid if market conditions dictate the need for petroleum products instead of petrochemicals.

The recycle riser is an external, cold wall riser similar to the primary riser. Products produced from both risers merge in the disengager vessel and travel as a common stream to the main fractionator.

Yields: The following yields were produced from a pilot plant using a hydrocracked gasoil feedstock:
Yields, wt% Run A Run B Run C Run D
Ethylene 3.2 3.9 6.4 8.2
Propylene 16.0 18.7 19.1 21.5
C5+ gasoline 37.9 28.8 26.2 25.0